The present invention relates to a driving system which is designed for use in various types of machines, such as combustion engines, pumps, compressors and the like.
The driving system according to the invention comprises a housing having a spherical hollow space, a rotatable main shaft, a driving means drivingly connected to the main shaft and a piston construction connected to the driving means, where the the piston construction is rockable backwards and forwards in the hollow space relative to a stationary wall portion in the hollow space and where one end of the driving means which participates in the rotary motion of the main shaft, is pivotally mounted in the main shaft about a pivotal axis which forms an acute angle with the axis of rotation of the main shaft.
Various driving systems of the afore-mentioned kind are known. There are employed a housing with a spherical hollow space, a rotatable main shaft and one or more pistons which are moved backwards and forwards in a forced rocking motion in the spherical hollow space, where the piston/pistons constitute a driven or a driving component of the driving system.
In DE 466 916 there are employed a pair of semi-spherical chambers on opposite sides of a stationary, first partition plate, which extends radially, that is to say across the rotational axis of the driving system centrally in the spherical hollow space. A rigid main shaft part passes through the spherical hollow space and is rotatably mounted via opposite, mutually aligned shaft pins at opposite ends of the housing. The shaft pins carry their respective laterally displaced, globular cup-shaped transition portion having an intermediate centre pin (driving means), which extends obliquely of the rotational axis of the main shaft. The centre pin is rotatably mounted internally in a piston construction consisting of a pair of conical pistons. The pistons are subjected to an unrolling motion on opposite sides of such a first, radially extending partition plate in their respective semi-spherical chambers. In each semi-spherical chamber two work chambers are defined by means of a second, axially extending partition plate, which connects conical portions of the pistons to each other and which passes through a slot in the first radially extending partition plate, something which creates special sealing problems in between the partition plates.
In U.S. Pat. No. 4,938,025 a similar system is shown, where the second partition plate is avoided and simultaneously the sealing problems which accompany such a through-passing partition plate are avoided. Instead the first partition plate is rockably mounted about a rocking axis, which extends across the rotational axis of the main shaft.
In both of the of afore-mentioned known solutions, where pistons are employed, which are subjected to combined rocking and pivotal movement, one is dependent upon the pistons being subjected to a seal-forming unrolling movement along the associated (first) partition plate. In practice it is difficult to ensure precise sealing via the pistons, since during use there will necessarily occur significant wear between the partition plate and the pistons, by the very fact that the pistons are rolled directly against the partition plate.
In U.S. Pat. No. 5,147,193 a solution is shown, where said seal-forming unrolling motion is avoided. Instead a sliding sealing abutment is employed between the pistons and the partition plate. The main shaft part comprises a rotatable, axially extending partition plate, instead of the radially extending, that is to say the transversely extending partition plate. Together with the partition plate there is rotatably mounted a piston construction comprising a pair of mutually rigidly connected ball segment-formed, that is to say orange boat-formed pistons. By this solution the combined rockable and pivotable motion of the pistons relative to a locally arranged partition plate is avoided. This is achieved by allowing the partition plate and the pistons to rotate jointly and by allowing in addition the rotatable pistons to be set in a rectilinear rocking motion relative to the rotatable partition wall.
The piston construction during its rotational movement is forced into a rocking motion backwards and forwards relative to the partition plate via a stationary journal and a rotatable control member, which is moveable in an oblique plane relative to the rotational axis of the main shaft. The piston construction is subjected to considerable rocking movement relative to the partition plate and in addition participates in the rotational movement together with the partition wall. It is a significant practical problem that large rotational forces occur centrally in the rotor member via the stationary journal and the associated rotatable control member.
In U.S. Pat. No. 1,434,741 a pump is shown having a rotatable main shaft, which is connected to a disc-shaped piston via a piston rod rigidly connected to the piston, the longitudinal axis of which extends obliquely of the rotational axis of the main shaft. A stationary pump housing is employed having a part-spherical, central hollow space, which spans over an arc angle of about 30xc2x0 relative to a spherical centre point. The hollow apace is divided by means of a stationary, axially extending partition plate, which passes through the piston via a transversely extending slot in the piston. The partition plate forces the piston into a combined rocking and pivoting movement relative to a conical stop in the surrounding pump housing. Consequently in a corresponding manner as in DE 466 916 one is dependent upon a complicated sealing abutment in a slot between two relatively moveable parts, of which the piston executes a combined sliding and rolling off movement. One end of the piston rod extends at right angles to the disc-shaped piston, while the opposite end of the piston rod, which participates in the rotational movement of the main shaft, is pivotally mounted in a head portion of the main shaft part, eccentrically about the rotational axis of the main shaft. Consequently one is compelled to employ a relatively narrow hollow space in the pump housing in combination with the stationarily arranged partition plate.
With the present invention the aim is a constructionally and operatively favourable solution, which provides a simple piston movement and minimal sealing problems.
As the state of the art in the area is taken the particular starting point of the solution according to U.S. Pat. No. 1,434,741. Inter alia in this connection the aim is to employ a considerably larger spherical hollow space than in the solution according to U.S. Pat. No. 1,434,741 plus avoiding the axially extending partition wall and the sealing problems connected therewith.
The driving system according to the present invention is characterised in that the piston construction, which comprises a pair of mutually rigidly connected pistons, is rockable relative to the surrounding housing about a first rocking axis, which passes centrally through the spherical hollow space at right angles to the rotational axis of the main shaft, that the piston construction is rockable towards and from an intermediate, stationary wall portion, which projects radially inwardly into a first hollow space section of the spherical hollow space and divides the hollow space section into two opposite work chambers, that the other end of the driving means is rockably mounted in the piston construction about a second rocking axis, which extends at right angles to the first rocking axis, the first and second rocking axes crossing the rotational axis of the main shaft at a common crossing point centrally in the spherical hollow space.
According to the invention three parts moveable relative to each other are employed instead of two parts moveable relative to each other according to the known solution, as shown in U.S. Pat. No. 1,434,741.
In the known two-part solution the piston is subjected to a rolling off movement, that is to say a combined pivoting and, rocking movement, relative to a stationary surface, which extends across the rotational axis of the main shaft, while with the equivalent three-part solution according to the invention the piston construction is subjected to a simple, rectilinear rocking movement, that is to say a pure rocking movement, relative to a stationary, centrally arranged, stop-forming partition wall.
In this connection two rocking axes are employed according to the invention, of which the one is arranged between the piston construction and the surrounding housing and the other between the piston and the main shaft via a separately moveable driving means, instead of the rigid connection between driving means/piston rod and piston in the known solution according to U.S. Pat. No. 1,434,741.
According to the invention the associated pistons of the piston construction are rocked about in a rocking plane, which extends at right angles to the stationary partition wall in the spherical hollow space. By means of the simple, pure rocking movement of the piston construction a relatively simple sealing off of the piston construction is achieved, based on sliding seals between the piston construction and the stationary inner walls of the spherical hollow space. In addition complicating rotational forces are avoided in the piston per se. In that the partition wall free endingly projects axially inwardly towards the piston construction, a simple slide seal can in addition also be employed between the piston construction and the partition wall.
The afore-mentioned simple rocking movement and simple sealing off is ensured by the driving means being rockably mounted in the piston construction on the side of the piston construction which faces away from the stationary partition wall. This means that the work chambers of the first hollow space section are easy to seal of f relative to the stationary partition wall and relative to the piston and the surrounding inner wall of the first hollow space section respectively.
According to the invention provision is made for the work chambers of the first hollow space section to be defined between the rockable piston construction and a stationary housing portion, the stationary partition wall included.
This means that the rocking movement of the piston construction in the first hollow space section can be sealed off in a simple and dependable manner, so that leakage of gas medium can be effectively prevented from the first hollow space section to the second hollow space section or vice-versa. Consequently there is the opportunity to use and design the second hollow space section more or less independently of the first hollow space section.
According to a particular aspect of the present invention the driving system is further characterised in that the pistons of the piston construction constitute the main pistons of the driving system, which form a part of the first hollow apace section, while the driving means constitutes an auxiliary piston, which forms a part of the second hollow space section, the driving means being disc-shaped and dividing the second hollow apace section into two associated auxiliary chambers.
According to the invention the second hollow space section is mainly formed by a rotatable housing part, which is directly connected to the main shaft, the rotatable housing part including a rotary bearing for the associated guide pin of the driving means. By this the driving means can be received in a rotating second hollow space having a backwards and forwards rocking movement relative to the rotatable housing part, so that the driving means can form an auxiliary piston having associated piston movement in the rotatable housing part.
The auxiliary piston can be employed for various auxiliary functions in connection with the main functions of the main pistons, but without being dependent upon the functions of the combustion chambers, as will be evident from the following description.